[mikethedruid]

well, Tom, here in the Providence area we have a number of strong FM stations so that really isn't the problem, and I am using the original line cord antenna over my new SPT1 18-2 line cord. I am pretty sure the antenna is not the real problem here. and, as I said, I AM receiving 2 stations weakly but understandably, and three hisses that sound like they want to be stations. I am going to go through the full checkout on the set, and a full alignment. Gotta build some new test cables first. What joy !

[mikethedruid]

well, things are improving.. have been going through the troubleshooting guide step by step... found a bad resistor in the FM section.. I think it sets a bias... anyway... replaced it and now can get all the local FM stations clearly, but as yet not very loud compared to the AM performance. So I will continue with my hunting.

I have a serious question. I clipped out Z404, and replaced it with a .01mf cap... but I am wondering if some of my problems now might be from replacing it without that makeshift inductor. Any thoughts ? Has anybody else just replaced it with a cap ? What were the results ?

[Mondial]

Z404 was designed to be series resonant at the IF freq and without the inductance you may get insufficient bypassing and oscillations. After all, why would Philco go to the trouble of winding wire around the .01 cap if it was not necessary?

I left Z404 as is in my radio, as there is no significant voltage across it and it tested low for leakage. You might try winding an equivalent amount of wire around the replacement capacitor and see if it makes a difference

[mikethedruid]

I am taking a little break now that I have the radio working well on AM and SW, and working on FM too. Here is a video showing it's current state... https://www.youtube.com/watch?v=dw7OrNI9qF8 . I am tired after almost a week of putting between 8 and 10 hours a day on the radio, so now that it's working pretty well, I am going to enjoy it a bit before I do more.

[mikethedruid]

LOL... I have the chassis back out of the cabinet, and am going to replace Z404 with a replica I made by wrapping paper around a .01 cap to which I soldered, close to the body, a piece of #24 stranded insulated wire. I wrapped the cap with paper to increase the diameter and length to approximate that of the original .01 paper cap. I had measured the wire to approximate the length of one leg of a TV rabbit ear, which seems to be about the length of the wire wrapped on the original, if not a bit more. We'll see if this makes a difference. I am also going to replace a number of resistors that set various voltages in the power supply and the bias voltage dividers for the FM section. I really think the set can perform better on FM than it is now. I am going to wait to start the work until I have all the resistors in before I begin again. We shall see.

[klondike98]

That was a short break Mike!

[mikethedruid]

Well I replaced Z404, and R401 which is the 1 meg right beside it. Figured I may as well while I was at it. I also replaced R418, R419, R303, and R301. No noticeable change yet. Waiting for some resistors to come in still, 56K, and 22 ohm for R305 and R306, as well as the 2 watt resistors for the main voltage divider. LOL, at least things did not get any WORSE, AM and SW are still very good, and FM is receiving a lot of local stations, but the volume output is still low. I suspect R305 which is reading 62K or even more likely R306, which reads very oddly with my multimeter, not holding any consistent reading but bouncing between 17 and about 25 ohms. It does this with the FM1000 pulled from the circuit, which lifts one leg in effect. Something very odd there, but, since I don't have a 22 ohm 1/2 watt 5% on hand, I'll have to wait until my resistor order comes in to replace it.

Knowing something about FM, and how it works, the volume I am receiving from the stations I am picking up should NOT be dependent on the amplitude of the signal being picked up, but rather how far from the basic tuned frequency the signal varies up and down. I suspect that the output signal fed into Z403 is low, and that may well be from either of those resistors, so I shall live in hope and wait until they arrive.

[mikethedruid]

LOLOL... deoxit on the multimeter rotary switch contacts cleared up the variable readings.... R305 now read a solid 62.8K now and R306 is a solid 28.8 ohms. I looked around again in my parts, and found a 56K 5% half watt, and replaced R305. Seemed to lend a very slight improvement.

[tom.seeger]

I hate to sound like a broken record, but could you try making a small FM dipole to pin on the wall behind the radio? You just need 6 or 7 feet of line cord split at the end to make a 56 inch dipole. It may be all the radio needs.
I have restored a dozen 1950s FM radios, the ones with built in antennas just don't work as well as with a small external antenna.

[Warren]

The antenna sounds like an easy thing to try if nothing else just to rule it out or give you a hint on what the problem might be. Couldn't hurt.

[mikethedruid]

With resistors that set voltages going to the FM 1000 more than 25% off, I am going to replace them first, before going to another antenna.

[mikethedruid]

FINALLY !!! I replaced C301 and R301 which gave minor improvement. Same with R306. Replaced R302 and things improved a good bit. Now have more volume out of the FM, more like what it ought to be.. I also got in the last of my resistors... the 2 watt 15K and 18K for the main power supply. Put them in, and re-tweaked things... now the radio is about as good as it will get. .... Hmmmm.... now which of my radios shall I restore next ? Maybe my Transitone PT-66...

[klondike98]

[mikethedruid]

just noticed a discrepency in the 48-482 bulletin... C 300A in the parts list is listed as a 15 mf cap ! In the schematic it is listed as a more realistic 15mmf. LOL... that's how much I have racked my brain over this thing.

[mikethedruid]

I knew that FM was not giving me the audio out it should have. I went back over the whole FM area around the FM1000. Found the problem. It was my OWN bonehead mistake. Instead of wiring C 304 to the 6th terminal from the bottom in the diagrams, to the junction with R302 and C305, I had wired it to the 7th terminal. I'm surprised it worked at all. I corrected this mistake; and, while at it, replaced C305 with an 820mmf and a 680mmf mica condenser in parallel to replace the 1500mmf mica condenser. FM was immediately a LOT more powerful in its audio... too powerful by far, and I had to re-tune the Z300. Once that was done, FM is excellent ! Volume on the local stations is now up there with the AM band, and the sound quality is fine too. I am now finally satisfied with the restoration of this radio.